Correct assessment about abs, more than one way to skin a cat. I'm enjoying
@Kforcer 's part of the discussion. There is some validity to the viewpoint that heavy spinal loading can leave one with a blocky looking waist, less V taper when viewed from the front, but I think that is not so specific to the rectus abdominis itself but rather more from the other core muscles, obliques and transverse abdominis.
Building muscle one way or another sounds like it will help your cause in your case it would probably be considered more "sports specific" to go with those other exercises.
Fats vs Carbs. I think it's important to satisfy the bodies minimum for fats, hormonal and joint health come to mind for an athlete, so that number reflects that for your size and you shouldn't go lower. Make sure it includes a bunch of the "good" fats. While you don't really need any carbs they are the most efficient fuel for intense exercise, most people like them and seeing as
The P and F have minimums they naturally become the easiest macro to modulate for weight gain or loss. Plus you can make choices about type of carbs to take in with regard to activity timing.
You absolutely can change the F and C ratio to your liking but respect the F minimum and the total cal number, remember that Fats have about 9 cal per gram while Carbs have about 4.